1. Field of the Invention
The present invention relates to a bandgap reference voltage generating circuit, and more specifically to a bandgap reference voltage generating circuit having an elevated response speed.
2. Description of Related Art
In the prior art, since a voltage for driving an integrated circuit and others is required to be a stabilized reference voltage, a bandgap reference voltage generating circuit is used. Referring to FIG. 1, there is shown a circuit diagram of one example of the prior art bandgap reference voltage generating circuit.
The prior art bandgap reference voltage generating circuit shown in FIG. 1 includes first, second and third unitary circuits 1A, 2A and 3A, and is supplied with a power supply voltage Vdd to generate a reference voltage Vo determined by a band structure of a semiconductor by causing n-channel field effect transistors (FET) N1 and N2 of the first and second unitary circuits 1A and 2A to operate in a weak inversion condition.
Namely, assuming that a junction area ratio between diodes D1 and D2 is 1: N, and a resistance ratio between resistors R and xR is 1: x, the circuit output voltage Vo in a stabilized condition becomes Vf+(.times.kT/q).cndot.1nN, where Vf=(kT/q).cndot.ln(n.sub.d /n.sub.i), k is Boltzmann constant. T is absolute temperature, q is elementary charge, n.sub.i is intrinsic carrier density of the n-type semiconductor, and n.sub.d is donor density.
However, the above mentioned prior art bandgap reference voltage generating circuit has a problem that when a power supply is powered on, a gate potential of the FETs does not become definite, with the result that the stabilized reference voltage Vo cannot be quickly obtained.